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Re: [PATCH] Add missed adjustment to label_nuses in reload.
- From: Jeff Law <law at redhat dot com>
- To: Marcus Shawcroft <marcus dot shawcroft at arm dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Wed, 04 Jan 2012 12:21:56 -0700
- Subject: Re: [PATCH] Add missed adjustment to label_nuses in reload.
- References: <4F045D38.7060204@arm.com>
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On 01/04/12 07:07, Marcus Shawcroft wrote:
> Reload (find_reloads) has code that can replace a register with a
> label_ref when presented with RTL of the form:
>
> (set (reg) (reg) (notes (rtx_equal (label_ref)))
>
> Label references are initially counted in jump.c:mark_all_labels()
> and friends. This code traverses the RTL and counts each observed
> label_ref. The code inserts REG_LABEL_OPERAND or REG_LABEL_TARGET
> as appropriate. Notes are not traversed therefore the (rtx_equal
> (label_ref)) shown above is not treated as a reference.
>
> Instruction deletion, in cfgrtl.c:delete_insn() does not
> re-traverse the RTL, The code traverses only the notes looking for
> REG_LABEL_OPERAND and REG_TARGET_OPERAND notes in order to count
> down the label_nuses field.
>
> The code in reload.c:find_reloads() converts a register to a
> label_ref and inserts the associated REG_LABEL_OPERAND but does not
> adjust label_nuses, this may result in the inappropriate deletion
> of a live label.
>
> This issue was discovered during the development of the ARM aarch64
> gcc backend and results in an ICE due to deletion of a live jump
> table.
>
> The issue has not been re-created on another target. The proposed
> patch has been regressed on x86 (and aarch64).
>
> Proposed ChangeLog entry below, patch attached:
>
> 2012-01-04 Marcus Shawcroft <marcus.shawcroft@arm.com>
>
> * reload.c (find_reloads): Adjust LABEL_NUSES on REG_LABEL_OPERAND
> insertion.
Approved after you fix some minor fomatting nits. Your code has:
++ LABEL_NUSES(XEXP (substitution, 0));
The line should be:
++LABEL_NUSES (XEXP (substitution, 0));
No space between autoincrement operator and its operand.
Space before the open paren of the XEXP
Thanks,
Jeff
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